Modeling%20of%20microscale%20variations%20in%20methane%20fluxes

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Modeling of microscale variations in methane
fluxes

• Anu Kettunen
• Jan 17th, 2003

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Solar energy and
cycling of elements
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Natural green house phenomenon

• Atmosphere ? surface temperature of Earth ca
  30oC higher than without atmosphere
• Green house gases prevent Solar energy from
  escaping from Earth
• H2O, CO2, CH4, N2O, CFC compounds

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Human activities

• Use of fossil fuel etc. human actions increase
  green house gas concentrations enhances green
  house phenomenon ? climate change

Robert T. Watson, IPCC chair
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Future climate

• On average warmer
• Regional differences
• Precipitation patterns
• Likelihood for extreme events (drought, storms)
  increases

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Mires

• Northern mires carbon sinks during last millenia,
  huge amount of carbon in peat
• Sources of green house gases (CO2 ja CH4)

• Important to understand role of mires in carbon
  cycle

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Methane

• CH4 important green house gas
• Concentration increases ca 1 per year
• Wetlands (20-30 ), rice paddies, ruminants,
  landfills, artificial lakes

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Research problem

• Previously no satisfactory description of spatial
  and seasonal variations in methane fluxes
• Growing season measurument CH4, T, WT etc. from
  different mire surfaces
• Methane production and oxidaton potentials
• Process model connects methane flux to vegetation
  cover, photosynthetic cycle and peat thermal and
  moisture conditions

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Process model
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Model predictions
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Fresh carbon, NPP and T

• Model sensitive to fresh carbon
• If T ja CO2 ? ? NPP ?
  ? substrate ? ? CH4 ?
• If only T ?? CH4 ? less

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Transport of oxygen to peat

• The more sedges transport oxygen to peat, the
  lower the CH4 flux
• If methane oxidation ? ? CH4 ?

Change in transport capacity of sedges
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The effect of drought

• Long dry periods ? methanogens ? ? CH4 ?
• If gt 4-6 week drought, no recovery even after
  rains come

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Main contribution of the thesis

• Simulation model for CH4 fluxes from different
  mire surfaces ? CH4 fluxes from boreal mires can
  be predicted under current and future climate
• Increased understanding
• Connection to general circulation models